Researchers at Imperial College London have devised a system for monitoring mortality rates which could help to alert authorities to crimes such as the murders committed by GP Harold Shipman and also provide useful feedback on the overall quality of care. However, they caution that data quality improvement is essential.

The study, published in the Lancet (registration needed), was funded by the Shipman Inquiry which has found that there is little monitoring of deaths in general practice.

The researchers started by extracting seven years of mortality data from 1993-9 from the statutory death register held by the Office for National Statistics. They then linked the data with general practices’ lists of patients held on five health authority information systems, including West Pennine, where Shipman worked.

With use of the National Health Authority Information System (NHAIS), deaths were linked through patients’ NHS numbers or, if these were not available, through other details, to provide a family physician, practice and senior partner code on each mortality record, together with an NHSAIS date of death field (for quality comparisons).

The products of the researchers’ work were a set of cumulative sum charts. On such charts thresholds for deaths can be set which, if crossed, could indicate a potential problem. Dr Shipman registered above the thresholds tested – but so did a small number of other GPs. The researchers say that it is too early to have formal feedback but that these other doctors’ results are probably explained by factors such as poor data quality or case mix – or both.

Asked how such a system could be developed on a national scale, Dr Paul Aylin, one of the study’s authors, told E-Health Insider: “I think I would see it as a national service – actually doing the linkage and running the analysis – but I think the primary care trusts would have a place in interpreting the charts and acting on them.”

He said information staff at local level may have a role in looking behind the charts and finding explanations for a physician crossing the threshold for investigations. By no means all “above threshold” alerts can be explained in clinical terms and Dr Aylin said data quality could be a problem in some cases.

The researchers conclude: “We envisage cumulative sum charts being used as a governance tool for monitoring performance since they enable a first pass analysis of the data and can highlight units with unusual outcomes. We caution, however, that the charts cannot by themselves shed light on the reasons for apparent poor performance.”

They say a paradigm shift is required is required in attitudes to performance monitoring by health professionals, the public and the media. Performance monitoring should be used as a starting point for an audit and learning opportunity rather than recrimination.

The paper’s findings will be considered during a series of seminars being held by the Shipman Inquiry in October and it seems likely that the Inquiry will make recommendations on a system to monitor mortality rates.